A note on the characterization of bismuth black by Raman microspectroscopy

Inspired by the discovery of bismuth metal used as a pigment in a fifteenth century illuminated manuscript, the identification of bismuth compounds by Raman spectroscopy is investigated. Raman spectra of bismuth metal powder, bismuth (III) sulfide (Bi2S3) and bismuth (III) oxide (α‐Bi2O3) are presented. The influence of excitation laser wavelength is explored, along with the laser‐induced oxidation of bismuth to α‐Bi2O3 and β‐Bi2O3. The implication of these results with respect to the selection of appropriate analytical protocols in the investigation of bismuth pigments in works of art is discussed. Copyright © 2009 John Wiley & Sons, Ltd. Raman spectra of bismuth powder as a function of excitation wavelength are presented. Bands at 70 and 97 cm−1 are attributed to bismuth metal, while bands at higher wavenumbers (appearing at shorter excitation wavelengths) are due to surface oxides. The implications of laser‐induced oxidation for the accurate detection of the pigment bismuth black in works of art are discussed.